(1) Field of the Invention
This invention relates to small arms ammunition, and more particularly to bullets particularly useful in common calibers of centerfire pistol and revolver (collectively “pistol”) ammunition.
(2) Description of the Related Art
A variety of cartridge sizes exist which may be used in pistols, rifles or both. Common pistol ammunition rounds include: .380 Automatic (also commonly designated 9 mm Kurz), 9 mm Luger (also commonly designated 9×19 and 9 mm Parabellum), .40 Smith & Wesson (S&W), 45 Automatic (also commonly designated Automatic Colt Pistol (ACP)) and 10 mm Automatic rounds. General dimensions of pistol rounds are disclosed in Voluntary Industry Performance Standards for Pressure and Velocity of Centerfire Pistol and Revolver Ammunition for the Use of Commercial Manufacturers ANSI/SAAMI Z299.3-1993 (American National Standards Institute, New York, N.Y.), the disclosure of which is incorporated by reference herein as if set forth at length.
A newer round, the .357 Sig is also gaining acceptance.
After many decades of use of the .45 ACP round, in the 1980's the US Army adopted a 9 mm Luger full ogival, pointed, full metal case or jacket (FMC or FMJ) round as the standard round for use in military sidearms. The parameters for the M882 9 mm Luger rounds purchased by the US military are shown in United States Military standard MIL-C-70508, the disclosure of which is incorporated by reference in its entirety herein as if set forth at length.
Historically, pistol bullets have been of all lead or of jacketed lead constructions. More recent developments include various dual-core bullets and monoblock bullets. Key examples of the former are Nosler Partition® bullets (trademark of Nosler, Inc. of Bend, Oreg.). The Nosler Partition-HG™ bullet is a handgun hunting bullet formed by impact extruding a brass body with a transverse web separating front and rear compartments and then installing lead cores in such compartments. Examples of the monoblock bullets are found in U.S. Pat. Nos. 5,760,329 and 6,148,731 and EP0636853.
It is common practice today in the United States and Europe to evaluate a projectile's performance against various barriers using gelatin as a simulant for tissue. Particularly in law enforcement cartridges, projectiles are tested against a ballistic gelatin block to determine a projectile's ability to provide adequate penetration and incapacitate a threat. In the United States projectiles are commonly evaluated against bare gelatin, heavily clothed gelatin, and gelatin covered with four layers of denim. One series of test events disposes a sheet of steel, wallboard, plywood, and/or auto glass as a barrier ahead of the gelatin block. Specific exemplary test events utilized to evaluate projectile performance are:
Test Event 1: Bare Gelatin
The gelatin block is bare, and shot at a range of ten feet (3.0 m) measured from the muzzle to the front of the block.
Test Event 2: Heavy Cloth
The gelatin block is covered with four layers of clothing: one layer of cotton T-shirt material (48 threads per inch (18.9 threads/cm)); one layer of cotton shirt material (80 threads per inch (31.5 threads/cm)); a ten-ounce down comforter in a cambric shell cover (232 threads per inch (91.3 threads/cm)); and one layer of thirteen-ounce cotton denim (50 threads per inch (19.7 threads/cm)). The block is shot at ten feet (3.0 m) measured from the muzzle to the front of the block.
Test Event 3: Four Layers of Denim
The gelatin block is covered with four layers of denim material (thirteen-ounce cotton denim −50 threads per inch (19.7 threads/cm)). The block is shot at ten feet (3.0 m) measured from the muzzle to the front of the block.
Test Event 4: Steel
Two pieces of 20 gage (1 mm (equivalent to 0.0396 inch)thick ) by six-inch (15 cm) square hot rolled steel with a galvanized finish are set three inches (7.6 cm) apart. The gelatin block is covered with light clothing and placed eighteen inches (45.7 cm) behind the rearmost piece of steel. The shot is made at ten feet (45.7 cm) measured from the muzzle to the front of the steel. Light clothing is one layer of the above described cotton T-shirt material and one layer of the above described cotton shirt material, and is used as indicated in all subsequent test events.
Test Event 5: Wallboard
Two pieces of half-inch (1.27 cm) thick, six-inch (15.2 cm) square standard gypsum board are set 3.5 inches (8.9 cm) apart. The gelatin block is covered with light clothing and set eighteen inches (45.7 cm) behind the rear most piece of gypsum. The shot is made at ten feet (3 m) measured from the muzzle to the front surface of the first piece of gypsum.
Test Event 6: Plywood
One piece of three-quarter inch (1.91 cm) thick, six-inch (15.2 cm) square AA fir plywood is used. The gelatin block is covered with a light clothing and set eighteen inches (45.7 cm) behind the rear surface of the plywood. The shot is made at ten feet (3 m) measured from the muzzle to the front surface of the plywood.
Test Event 7: Automobile Glass
One piece of A.S.I. (American Standards Institute) one-quarter inch laminated automobile safety glass measuring 15×18 inches (38.1×45.7 cm) is set at an angle of 45 degrees to the horizontal. The line of bore of the weapon is offset 15 degrees to the side, resulting in a compound angle of impact for the bullet upon the glass. The gelatin block is covered with light clothing and set eighteen inches (45.7 cm) behind the glass. The shot is made at ten feet (3 m) measured from the muzzle to the center of the glass pane.
Test Event 8: Heavy Cloth at 20 Yards (18.3 m)
This event repeats Test Event 2 but at a range of 20 yards (18.3 m) measured from the muzzle to the front of the block.
Test Event 9: Automobile Glass at 20 Yards (18.3 m)
This event repeats Test Event 7 but at a range of 20 yards (18.3 m) measured from the muzzle to the front of the glass. The shot is made from straight in front of the glass without the 15 degrees of offset.
These test events were developed to duplicate what are considered to be field scenarios commonly encountered in law enforcement. For testing purposes, generally five shots are fired in each test event. For each shot, penetration is measured and recorded. The projectile is then recovered from the gelatin block, weighed, measured for expanded diameter, and information recorded. It is desirable for a projectile to retain a high percentage of original bullet weight to promote at least a certain amount (e.g., twelve inches (30.5 cm)) of penetration to reach what is considered to be the vital areas of a target. It is also desirable for a projectile to yield adequate expansion and not allow penetration greater than a greater amount (e.g., eighteen inches (45.7 cm)) to reduce the risk of collateral damage. Results of various bullet configurations are then compared for optimum performance.
Of the test events listed, auto glass probably presents the most challenge in developing a bullet that will retain a high percentage of original bullet weight and yield adequate penetration while still providing consistent, reliable performance in the other test events/encounters. Bullets penetrating auto glass are subjected to very high abrasive and cutting forces imparted directly to the bullet exterior (e.g., to the jacket of a jacketed bullet). These forces act in conjunction to literally cut and strip the bullet jacket from the core material. It is common for the jackets of conventional jacketed projectiles to separate from the core material during penetration of auto glass, jacketed hollow point (JHP) and FMJ styles alike. It is very difficult to produce JHP bullets that perform well in all of the test events described.
Environmental legislation and regulations in the United States have increased in recent years, initiating development of lead-free, nontoxic, bullets for training purposes. These bullets are typically of a FMJ or soft point configuration. Although toxicity has been more of a concern in the area of training ammunition, future regulations may dictate the development of lead-free, nontoxic, duty rounds for law enforcement in the United States. This is already a reality in Europe where lead-free monoblock bullets such as those shown in U.S. Pat. No. 5,760,329 and EP 0636853 have entered service.